1. Field of the Invention
This invention relates to cylinder assemblies and more particularly to a valve stem retainer particularly suited for use with a master cylinder of the center feed type.
2. Description of the Prior Art
A master cylinder of the center feed type includes a cylinder defining an axially extending pressure chamber and including a reservoir port proximate the front end of the cylinder for communication with a fluid reservoir; a piston slidably positioned in the cylinder and adapted for coaction with a piston rod extending into the rear end of the cylinder; a valve assembly in the pressure chamber including a valving member proximate the reservoir port and a valve stem secured to the valving member and extending axially rearwardly in the pressure chamber; and a retainer on the front end of the piston connected to an enlarged head portion on the free end of the valve stem.
In operation, when the piston is moved forwardly in the cylinder by actuation of the piston rod, the pressure fluid forwardly of the piston moves the valving member into seating engagement with the reservoir port and the valve stem moves axially into a central axial bore in the front end of the piston to allow the piston to continue to move toward the front end of the cylinder to discharge pressure fluid from the cylinder through a suitable discharge port. As the piston thereafter moves rearwardly in the cylinder upon retraction of the piston rod, the valve stem slides axially in the central bore in the piston until the piston approaches the end of its return stroke at which time the retainer on the piston engages the head portion of the valve stem and pulls the valving member out of seating engagement with the reservoir port to establish fluid communication between the reservoir and the cylinder pressure chamber to ensure total filing of the pressure chamber behind the retreating piston. An example of a center feed master cylinder of this type is shown in U.S. Pat. No. 4,407,125 assigned to the assignee of the present invention.
Whereas center feed master cylinders of this type provide a relatively compact and efficient overall package, assembly and disassembly of the cylinder is difficult and time consuming, in part because of the complex procedure required to assemble and disassembly the retainer to and from the head portion of the valve stem of the valve assembly.